React Native AI message streaming not working - messages appear all at once

[christiannwamba]

Problem Description

AI message streaming using @convex-dev/agent does not work on React Native Expo app. Messages appear all at once after AI completes generation instead of streaming incrementally character-by-character.

Environment

• Platform: React Native 0.76.9 (Expo ~52.0.46)
• Convex Version: ^1.25.2
• Convex Agent Version: @convex-dev/agent ^0.2.10
• Metro Config: Added unstable_enablePackageExports: true for package.json exports resolution
• Import Path: Using @convex-dev/agent/react (not /dist/react)
• Backend: Correctly configured with saveStreamDeltas: true and syncStreams()
• Other Clients: Web client using identical Convex backend works perfectly with streaming

Expected Behavior

1. Message status should transition: "pending" → "streaming" → "success"
2. useThreadMessages should receive streaming deltas from useStreamingThreadMessages
3. Text should appear incrementally as AI generates response
4. useSmoothText should animate text appearance character-by-character

Actual Behavior

1. Message status jumps directly: "pending" → "success" (never shows "streaming")
2. All messages have streaming: false field
3. Complete text appears instantly when AI finishes generating (no incremental updates)
4. messages object contains only ["results", "status", "isLoading", "loadMore"] keys - no streaming data

Diagnostic Logging Results

// What we observe:
[STREAM-CHECK] {
  resultsCount: 2,
  status: "success",
  streamEnabled: true,
  messageKeys: ["results", "status", "isLoading", "loadMore"],
  hasStreamsProperty: false,
  streamsValue: undefined,
  last3Messages: [
    { order: 1, streaming: false, status: "success" },
    { order: 2, streaming: false, status: "success" }
  ]
}

// Status progression observed:
[MSG-STATUS] { role: "assistant", status: "pending", textLen: 0 }
[MSG-STATUS] { role: "assistant", status: "success", textLen: 266 } // Full text arrives instantly

Key observation: streaming: false on ALL messages, and no streams property in the returned object from useThreadMessages.

Backend Configuration (Verified Working on Web)

// Backend saves deltas:
export const generateResponse = internalActionWithUser({
  handler: async (ctx, args) => {
    const result = await thread.streamText(
      { system: systemPrompt, messages: [toolMessage], tools },
      { 
        saveStreamDeltas: true,  // ✓ Enabled
        contextOptions: { recentMessages: 20 }
      }
    );
    await result.consumeStream();
  },
});

// Backend returns streams:
export const listThreadMessages = authorizedQuery({
  args: {
    threadId: z.string(),
    paginationOpts: convexToZod(paginationOptsValidator),
    streamArgs: convexToZod(vStreamArgs),  // ✓ Accepts stream args
  },
  handler: async (ctx, { threadId, paginationOpts, streamArgs }) => {
    const paginated = await chatAgent.listMessages(ctx, { threadId, paginationOpts });
    const streams = await chatAgent.syncStreams(ctx, { threadId, streamArgs });  // ✓ Syncs streams
    return { ...paginated, streams };  // ✓ Returns streams
  },
});

Client Usage

const messages = useThreadMessages(
  api.app.chat.listThreadMessages,
  selectedThreadId ? { threadId: selectedThreadId } : "skip",
  {
    initialNumItems: 50,
    stream: true,  // ✓ Streaming enabled
  }
);

const uiMessages = toUIMessages(messages.results ?? []);

// components/AI/components/MessageBubble.tsx
const [visibleText, smooth] = useSmoothText(text, {
  startStreaming: status === "streaming",  // Never true on React Native
});

Comparison: Web vs React Native

Web Client (Working):

• Uses identical backend queries
• Same useThreadMessages hook pattern
• Streaming works correctly
• Status shows "streaming" during generation
• Text appears incrementally

React Native Client (Broken):

• Uses identical backend queries
• Same useThreadMessages hook pattern
• Streaming does NOT work
• Status jumps from "pending" to "success"
• Text appears all at once when complete

Question

Is there a known React Native-specific limitation or configuration required for useThreadMessages streaming that differs from web? The fact that the web client works perfectly with the same backend suggests a client-side React Native issue.

Specifically:

• Does useStreamingThreadMessages work correctly on React Native?
• Are there any React Native-specific subscription/polling behaviors that might cause delayed delta arrival?
• Could there be a timing issue where deltas arrive after the message completes?

[ianmacartney]

Thanks for the report. I haven't heard reports of this - I'm not sure how react native handles situations like this differently than React. Are you seeing queries being called to list the messages & streams? You can investigate the websocket messages to see if the queries are being updated, to see if they're making it to react native or getting batched up for some reason?

[christiannwamba]

@ianmacartney I had to upgrade from Expo 52 to 53 and it resolved the issue. 53 and 54 depends a later version of web stream polyfill (>3.3.3). Streaming does not work if you use anything below that version.

[ianmacartney]

thanks for following up

…

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